The present invention relates to a method of controlling the speed of an arm of a disk drive and, more particularly, to a method of controlling the speed of parking the arm on a ramp.
A data storage disk drive consists of al least one disk on which data is stored, a read/write head mounted on an arm to read or write on the disk surface, and the necessary control circuits. The disk is rotated at a constant velocity by a spindle motor and the arm is moved over the disk surface to read from or write to different locations on the disk surface by a voice coil motor (VCM).
When there are no read or write operations for a relatively long time or upon power down of the disk drive, the VCM arm is traditionally parked towards the inner diameter of the disk. This is necessary to avoid any damage to the surface of the storage medium by physical contact with the read/write head. The storage area of the disk is generally made smooth to maximize the data density. If the arm is parked on the smooth surface, the spindle motor will experience more friction when it starts to spin the disk. To avoid this friction, the surface of the disk over which the arm rests can be made with a particular texture. This method of parking has two main disadvantages: the effective area that can be used for storage is reduced; and the read/write head will wear more quickly.
To avoid the problems mentioned above associated with parking the arm at the inner diameter of the disk, the arm can be parked away from the disk surface. The arm can be moved over a ramp at the outer edge of the disk. It is desirable to be able to actively control the speed of the arm to deliver the arm to the ramp as fast as possible without damaging the disk drive.
In accordance with the present invention there is provided a method of controlling the speed of an arm of a disk drive, including the steps of:
obtaining a feedback signal representative of the speed of said arm;
comparing said feedback signal with a predetermined command signal representing a command speed to determine an acceleration state of said arm; and
adjusting a drive signal for a motor to drive said arm at said command speed, said drive signal being adjusted, depending on said acceleration state, to drive said motor at a predetermined level.
The present invention also provides a system for controlling the speed of an arm of a disk drive, including:
feedback means for generating a feedback signal representative of the speed of said arm; and
drive means for comparing the feedback signal with a predetermined command signal representing a command speed to determine an acceleration state of said arm and for adjusting a drive signal for a motor to drive said arm at said command speed, said drive signal being adjusted, depending on said acceleration state, to drive said motor at a predetermined level.